19 Degrees Of Separation

Distributed across the entire web, though, are a minority of pages—search engines, indexes and aggregators—that are very highly connected and can be used to move from area of the web to another. These nodes serve as the “Kevin Bacons” of the web, allowing users to navigate from most areas to most others in less than 19 clicks.

Barabási credits this “small world” of the web to human nature—the fact that we tend to group into communities, whether in real life or the virtual world. The pages of the web aren’t linked randomly, he says: They’re organized in an interconnected hierarchy of organizational themes, including region, country and subject area. Interestingly, this means that no matter how large the web grows, the same interconnectedness will rule. Barabási analyzed the network looking at a variety of levels—examining anywhere from a tiny slice to the full 1 trillion documents—and found that regardless of scale, the same 19-click-or-less rule applied.

There isn’t yet a decent explanation for the 19-clicks rule — Barabási thinks it has something to do with the way pages on the Internet are grouped — but then again, there isn’t yet a decent explanation for the Six Degrees of Kevin Bacon rule, either. Of course, that popular movie trivia game (1) was itself inspired by the 1993 movie Six Degrees of Separation (2), which starred Will Smith, and does not feature Bacon. The movie was based on a 1990 play of the same name written by John Guare (3), and while it’s not clear where he got the idea (some say credit the Italian inventor Guglielmo Marconi), the earliest cited proponent of the theory is Hungarian novelist and poet Frigyes Karinthy (4) who is discussed in the 2002 book Linked by Albert-László Barabási (5) who today wrote about how many clicks separate web pages on the Internet (6).

(Image: A visualization of the billions of pages connected through the Internet by Opte Project.)